1. Field of the Invention
The present invention relates to a portable terminal having a calling function like a PHS (Personal Handyphone System) terminal, and more particularly to a portable terminal by means of which a user can enjoy sound data such as music in a stereo mode.
2. Description of the Related Art
Portable terminals represented by a portable telephone set such as a PHS (Personal Handyphone system) have exhibited very remarkable development and functional improvement and not only have a calling function but are very often designed as small-size information processing apparatus which can access various networks such as the Internet to upload or download data. Particularly, attention is attracted to reception and playback of videos and music by a radio terminal as a result of augmentation of compression and playback techniques of data.
For example, Japanese Utility Model Laid-Open No. 6958/1993 proposes an apparatus wherein a headphone stereo set and a portable telephone set are integrated. According to the proposal, if a telephone call terminates at the telephone set during playback of music by the headphone stereo set, then the ringing tone is played back preferentially so that the user may be notified of the telephone call termination with certainty. More particularly, according to the apparatus proposed, when music is not enjoyed with the headphone stereo set, a buzzer on a body panel of the telephone set emits sound similarly as in an ordinary portable telephone set, but when music is enjoyed, the headphone stereo set itself outputs a ringing tone so that the user may respond to the terminating call with certainty.
The apparatus of the proposal, however, is disadvantageous in that, when a telephone call terminates, if the volume of music being played back is very great or the ringing tone is confusing with music being played back, then the user is liable to miss the ringing tone or a considerable time is required until the user becomes aware of the ringing tone being outputted.
Thus, Japanese Patent Laid-Open No. 243358/1992 discloses an apparatus of the type described above wherein, if a telephone call terminates at the portable telephone set while the portable telephone set is in a music playback mode, then the playback of music is placed into a muting state and a voice signal of the other party of the terminating call is added by an addition circuit thereby to prevent a phenomenon that the voice signal cannot be heard well due to the music.
A further improved apparatus of the type described is disclosed in Japanese Patent Laid-Open No. 187060/1998. The apparatus includes a radio terminal and an earphone microphone unit, and if a telephone call terminates during playback of music, then the playback of music is interrupted and a ringing tone is outputted from the earphone microphone unit. Then, the radio terminal is automatically switched to a talking mode. This enables hand-free talking with the radio terminal. With the apparatus, however, if a telephone call terminates while the radio terminal body is accommodated in a bag or the like, then the radio terminal is switched into a talking mode immediately. As a result, the user cannot respond to the terminating telephone call for a considerably long time, and the telephone call may possibly be abandoned.
Thus, Japanese Patent Laid-Open No. 23115/1998 discloses an apparatus of the type described which responds to a telephone call rapidly if the telephone call terminates when music is enjoyed with a headphone while the radio terminal body is accommodated in a bag or the like. According to the apparatus, a terminating call response button and a clearing button are provided on a remote controller for the headphone. If a telephone call terminates, then music being played back is stopped and telephone conversation can be started when the user depresses the terminating call response button. Accordingly, if a telephone call terminates while the apparatus is accommodated in a bag or the like, the problem described above can be solved by depressing the terminating call response button when the radio terminal body is taken out. If the clearing button is depressed when the telephone conversation comes to an end, then the temporarily stopped playback of music can be started. The apparatus, however, is disadvantageous in that special hardware of the remote controller for the headphone must be prepared and therefore the production cost of the radio terminal is increased as much.
FIG. 7 shows part of a circuit of a radio terminal proposed as a countermeasure for solution of such problems as described above. Referring to FIG. 7, the radio terminal generally denoted at 100 includes a headphone 103 including a first speaker 101 and a second speaker 102, an apparatus body 104, and a headphone attachment terminal 105 for allowing connection between the headphone 103 and the apparatus body 104. An antenna 111 is mounted on the apparatus body 104. The apparatus body 104 has a radio telephone section, a stereo sound processing section, and a switching section disposed therein. The radio telephone section includes a transmission/reception circuit 112 connected to antenna 111, a voice processing circuit 113 connected to the transmission/reception circuit 112 for processing voice to be transmitted and received, a received voice amplification circuit 115 connected to the voice processing circuit 113 for amplifying received voice, and a transmission voice amplification circuit 116 for amplifying voice to be transmitted. The stereo sound processing section includes a stereo music playback circuit 117 for playing back stereo sound, and a first sound amplification circuit 118 and a second sound amplification circuit 119 connected to the stereo music playback circuit 117. The switching section includes a first changeover switch 121 and a second changeover switch 122. A ringer 123 for notifying a user of the radio terminal 100 of termination of a telephone call is connected to the transmission/reception circuit 112 of the radio telephone section.
In the radio terminal 100, output terminals of the first and second changeover switches 121 and 122 are connected to corresponding ones of the first and second speakers 101 and 102 through the headphone attachment terminal 105. The first and second sound amplification circuits 118 and 119 are connected to corresponding ones of music input side terminals of the first and second changeover switches 121 and 122. Accordingly, when the stereo music playback circuit 117 is playing back stereo sound, a music output for one ear outputted from the first sound amplification circuit 118 is inputted through the first changeover switch 121 to the first speaker 101, from which sound is outputted. Meanwhile, another music output for the other ear outputted from the second sound amplification circuit 119 is inputted through the second changeover switch 122 to the second speaker 102, from which sound is outputted similarly.
It is assumed here that a telephone call terminates while the user is enjoying music in this manner. In this instance, the transmission/reception circuit 112 of the radio telephone section controls the stereo music playback circuit 117 to decrease the sound volume in playback of music and controls the stereo music playback circuit 117 to generate particular sound so that a ringing tone is outputted from the first speaker 101 and the second speaker 102. However, when playback of music is not being performed, the ringer 123 notifies the user of termination of a telephone call. If the user depresses a predetermined button disposed at an operation section not shown of the apparatus body 104 in response to the termination of the telephone call to start telephone conversation with the other party, then the first and second changeover switches 121 and 122 are switched to the opposite contacts to those shown in FIG. 7. Consequently, the received voice amplification circuit 115 is connected to the first speaker 101 while the transmission voice amplification circuit 116 is connected to the second speaker 102.
As a result of the switching, a voice signal received by the transmission/reception circuit 112 and processed by the voice processing circuit 113 is amplified by the received voice amplification circuit 115 and then outputted from the first speaker 101. At this time, the user will remove the second speaker 102 from the ear, hold it with its hand and use it as a microphone. The voice uttered toward the second speaker 102 is amplified by the transmission voice amplification circuit 116 and processed by the voice processing circuit 113 and the transmission/reception circuit 112, and then signaled to the other party from the antenna 111.
For the radio terminal 100 shown in FIG. 7, special hardware of a remote controller for the headphone need not be prepared. Accordingly, the apparatus can be produced at a cost reduced as much. However, if a telephone call terminates, then the user removes the second speaker 102 of the headphone 103 from its ear and talks using the second speaker 102 as a microphone. Accordingly, the radio terminal 100 is disadvantageous in that it requires an operation of removing one of the speakers from the ear of the user and, if the other first speaker 101 is removed in error, then since the arrangement of the microphone and the speaker is reverse, the user cannot hear the voice of the other party nor can transmit its voice to the other party.
FIG. 8 shows a general configuration of a radio terminal which includes a stereo headphone microphone proposed to eliminate the disadvantages described above. Referring to FIG. 8, the radio terminal generally denoted at 200 includes a portable telephone set body 201, a playback unit 202 for a mini disk (MD) connected to the portable telephone set body 201, and a stereo headphone microphone unit 203 connected to the portable telephone set body 201 similarly. The stereo headphone microphone unit 203 is used in an apparatus disclosed in Japanese Patent Laid-Open No. 168534/1999 and other documents and includes a first earphone (or speaker) 205, a second earphone (or speaker) 206, and a microphone 207 disposed in the proximity of the second earphone 206. The stereo headphone microphone unit 203 is conventionally used popularly.
Where the stereo headphone microphone unit 203 described above is used, each time a telephone call terminates, the user need not remove one of the earphones or speakers from its ear, but may input voice to the microphone provided separately. However, where the stereo headphone microphone unit 203 is used, since the second earphone 206 and the microphone 207 are disposed at a short distance, improvement in echo path is difficult. Accordingly, the stereo headphone microphone unit 203 is disadvantageous in that sound outputted from the second earphone 206 is taken into the microphone 207 and transmitted as an echo to the other party of telephone conversation.
The stereo headphone microphone unit 203 is disadvantageous further in that, since a pair of amplification circuits are provided separately for a telephone and for playback of music and a switch for switching the amplification circuits must be provided, an increased number of parts are required and an increased production cost is required as much, similarly with the apparatus described hereinabove with reference to FIG. 7.
The stereo headphone microphone unit 203 is disadvantageous also in that, when playback of sound data of music or the like is proceeding with the radio terminal while the stereo headphone microphone unit 203 is used, if the stereo headphone microphone unit 203 is not removed, then the user cannot hear an external announcement well or cannot speak easily with people around the user.